In the padding of furniture, different types of foam are normally used, such as foam rubber, polyurethane, latex etc, in the outer layer bordering to the cover of the furniture which may be of textile, leather or a synthetic material. The padding of the seat of furniture, such as a seat in the chair, may for example lie over other types of spring systems, such as slats, spiral springs or rib springs, or the padding material may make out the entire suspension in itself.
It may be difficult to adapt the suspension of furniture to different users, and in such an adaptation must usually be performed as a consequence of the user's weight. A hard or soft suspension will be experienced differently in relation to how heavy the user is. However, it is difficult to adjust such suspension in an automated system without using spring material of different density and/or stiffness.
An accompanying problem concerns the structure of a seat in furniture, such as a chair or a sofa seat, wherein the padding normally should be harder towards the sides of the seat in order to provide support, and possibly softer towards the front edge in order to make it easy to sit down and get up, simultaneously as a flexible support is achieved when the user leans forward. In order to obtain such effects it has been common to provide different types of springs under the seat of the chair, or to build up the seat with different types of foam with different properties. However, it is difficult and expensive technically in production to perform such a build up, and several lines of production are necessary.
U.S. Pat. No. 6,755,475 discloses a cushion structure with several internal volumes created by inflatable containers. The containers provide free volumes in the mould during moulding and may be filled with foams of different property such as resilience, after the moulding of the cushion or at the same time, through pin holes. The technique is however complex and requires inflatable containers of varying sizes that will withstand hot liquid foam moulded around the containers. The precision of the size and position of the containers is also limited, and the combinations are limited to a minimum size.
DE 296 21 190 discloses a mattress comprising a foam material with channels running over the entire width of the mattress, the channels having an inverted T-shaped cross sectional shape. The channels may have different spacing and dimensions to provide varying resilience. However, variation in resilience will only be provided in the length direction of the mattress, and will not provide increased side support, such as needed in a seat.
From prior art, continuous holes in upper mattresses of foam or latex are known in order to provide ventilation of the mattress during use. GB 1 445 561 discloses a mattress of foam material with drilled cavities going through the mattress. The cavities are arranged in limited length sections with a varying density of holes per area to provide varying resilience over the length of the mattress. However, holes going through the foam product may lead to tearing the product during stress especially if the density of number of holes per area is high.
DE 200 19 161 discloses devices for mounding cavities into a foam element such as a mattress. The device comprises a stem connected to a main body with a larger dimension than the stem around which foam is moulded, the shape of the main body may be of different shapes. The device also comprises a cutting device for extracting the main body out of the cured foam after moulding. The cutting of the foam material after curing will however also degrade the product as it may give rise to rupture during use when subjected to stress.
Further, foam mattresses are known with even “wave top patterns” in order to increase the softness of mattresses in relation to the stiffness of the foam. However, no variation in the stiffness is provided by the padding in the different parts of the furniture where they are used.
Therefore, there is a need for a padding wherein the resilience of the padding varies locally, preferably with smooth transitions without straining the foam material causing ruptures. The padding should be produced in a simple, quick and cost effective manner, preferably integrated with modern elements for furniture.